Diaphragm-control mounting



Sept. 1%8, 1928. 1,684,701

c. M. HAYMAN DIAPHRAGM CONTROL MOUNTI NG Filed March 10, 1925 O/Mlwwfww nnaman Patented Sept. 18, 1928.

UNITED STATES PATENT oFFicE.

DIArHnAGM-oor'mor. MoUN'rrNo.

Application illed. March 10, 1925. Serial No. 14,861.

The invention relates in general to an improvement in the mountings for electromagnets used for controlling diaphragms in transinitters and otlier instruments used for generating or receiving sound waves, and the invention specifically relates to an mproveiiient in the electromagnets and mountings therefor in telephone receivers ofthe type at present used as the speaker iinit in -lo ud speakers coinmonly used in connection with radio receiving instruments.

More definitely defined the invention relates to tliat type of instrument wliere the vibrating diaphragin is stressed under tension by the action of a permanent inagnet and is caused to vibrate by or to produce vibrations inan electroinagnet by vibration of the diaphragm or by changes in current impulses seiit through the electromagnet. In such instruments it is required that the location of the controlling or controlled electromagnet poles with relation to the vibrating diaphragm be varied by each individual to suit his particular requirements and to produce the required synchronization between the electromagnet and the vibrating diaphragm. Under all conditions the poles of the electroiiiagnet are in close juxtaposition to the dia-- pliragin. ln other Words the air gaps between the poles and the diaphragm are required to be of small diinensions in order to obtain extreme sharpness in tuning.. In such constructions it is appreciated that the diinensions or rather the configurations of the air gaps are varied with each adjustment of the electromagnet relative to the diaphragm, and with each change in sag of the diaphragm when placed under its electromagnetic tepsion a change in the gap is made.

The primary object of the invention is to provide a simplified form of ladjustment which will permit of a micrometrical variation in the mean average depth of the air gap and which Will maintain the configuration of the air gap constant, or at least substantially constant, in the different bowed position of the flexed diaphragm and the air gaps are thus maintained with flat ends at the polepieces and diaphragm 'and at the same time the desired depth of air gap can be varied slightly.

Broadly I attain this phase of the inven- -tioii by positioning parallel to and opposite the diaphragm a spring bridge for holding the magnet pole pieces and which bridge Will be designed to have substantially the same yresiliency as the diaphragm so that it can be bowed in the same direction and in the same degree as the diaphragm is bent when distorted to place the same under tension. ln this way the active eiids of the pole pieces are at all times disposed parallel to the portion of the diaphragm opposite the same.

It is known in structures of this type to position the pole pieces in parallelism and opposite the central portion of the marginally supported diaphragin. With increased bowing of the diaphragm it is obvious that a progressively greater pulling force is required to increase the sag but such strong pull on the part of the magnet is not. required When the diaphra m is at or near its normally flat unfiexe position.

The present disclosure features compensated electromagnetic drawing efl'ects on the diaplragin and the parts are so proportioned and organized that with the one electromagnet, and even Which may have constant strength, as would be the case in a permanent magnet, the pull on the diaphragm can be modified automatically so as to meet the best .requirements necessary to provide the requisite degree of distortion of the diaphragm.

'll'his phase of the invention is attained by causing the active pole ends .to ,approach or sprung from ts normal positioneach other and to approach the highly flexible central Aportion of the diaphragm so that the lines of force connecting the pole ends are shortened and concentrated towards ,the center of the diaphragm.

lit is required of instruments of thetype under discussion that they be light in Weight and this is especially true When they are required to be easily ported as in the case of ear-pieces. On the other hand the spring bridge wliich carries the pole pieces Works most efiiciently When made of spring metal which is not easily flexed as when made of the same material as was used in forming the \iisually stiff diaphragmi.

D Accordingly, another object of the invention is to provide a Simplified form of controlpfortadjusting the tension on the pole pieces carrying spring bridge and to provide parts Which While sufiiciently rugged to perform its ofiice will not add materially to the ;Weight of the device nor necessitate the use v of a casing of umisiial dimensions or strength.

This phase of the invention is attained by passing the usual control screw loosel through the casing instead of'following the .usual practice of threading it through the casing vand engaging the screw by a nut accessible from the exterior of the casing and having a broad bearing surface on the casing and otherwise designed to distribute the strain incidentalto thetightenin up operation when flexing the spring bri ge.

Another object of the invention is tofprovide a simple and easily mani ulated orm of nut-lock for securingl the exed spring bridge in itsadjusted position.

Various other objects and advantages of.

the invention ;will be in part obvious from an inspection of the accompanying drawings and in part will be more fully set forth in the following particular description of lone form of device embodying.I my invention, and the invention also consists in certain new and novel features of construction and combinationof parts hereinafter set forth and claimed. In the accompanyin drawings Figure 1 is a view ta en axially through a preferred embodiment of the invention and showing the diaphragm and controlling electromagnet unflexed and in normal inoperative position.

Figures 2 and 3 are each transverse sectional views taken respectively on the, lines 2-2 and 3-3 of Figure 1 looking' in the direction indicated by the arrows; and

Figure 4 is a view similar to Figure 1 with some of the parts omitted and with .other parts shown diagrammatical and showing in exaggerated position the relation of the diaphragm and electromagnet when in operative position and both flexed under tension.

In the following vdescription and in the claims, arts .will be identified by specific names or convenience of expression but they are intended to be as generic in their application to similar parts as the art will.

permit.

In the drawings there is shown a cupshaped 'mechanism containing casino' 10 opened at one end and closing this end is a diaphragm 11 secured in place by means of a cover 12 in the present instance constituting a means for `securing the instrument to a loud speaking horn engaging the threaded throat 13. The casing and cover are preferably formed of molded composition and usual ring washers 14 are positioiied between the cover. Positioned within the chamber .15 formed between the diaphragm 11 and the bottom 16 of the casino' 10 is a replaceable inetallic unit 17vpreferalily energized to form a permanent lelectromagnet. This electromagnet includes a wide thin sheet metal spring plate 18 opposite ends 19 and 20 of which are rounded to fit within the cover 12 and rest respectively on shoulders 21 and 22 formed integral with the casing 10 adjacent the bottom thereof.. The spring plate 18 vforms a bridge which normally`extends parwaw allel to the diaphragm and to 'theflat bottom 16 as shown in Figure 1 but is designed to liave'its center bowed towards the bottom. as particularly shown in Figure 4. Mounted on the spring bridge and on o posite sides of its center are a par of pole pieces 23 and 24, L-shaped in elevation and each provided with an outwardly extending horizontal leg 25 secured to the sprin plate 18 by ascrew 26 and by a bolt 27. eiated nut 28 also constitutes a binding post. The two binding posts thus formed connecI the respective pole pieces with the external rircuit usual in such constructions.

The upstanding arm 29 of each of the pole pieces normally projects in parallelism to each other as shown in dotted lines in Figure 1 and extend laterally of the plane of the sprin bridge and terminate in each instance in a at en 30 positioned relatively close to but spaced a' short distance from the diaphragm to form the usual air gap 31. Each of the upstanding legs of the pole pieces is provided with the usual windings 32.

The center of the base. 16 is provided with an aperture 33 through which loosely extends a screw 34 the upper end of which is secured rigidly'and non-rotatably to the center of the spring bridge 18. Opposite sides of the screw are flattened as shown at 35 `Fi0ure 2) and the threaded portion is engaged externally of the casing by a relatively wide nut 36. The nut provides two circular flanges with their inner faces 37 and 38 extending' in a plane normal to its axis of rotation Yand co-acting to provide' a wide flat innerface for engaging the flat outer side 39 of the bottom of the casn It i understood from this construction that rotating the nut about the axis of the screw will cause vthe screw toadvance axially but without rotating and in this way adjustthe position 'of the spring bridge and with it the position of the pair of pole piece ends 30 relative to the diaphragm.

For the purpose of limiting the advance of the electromagnet pole pieces towards the his bolt with its assodiaphragmiJhe nut is secured against rotary movement yond 'a limiting position. For this purpose the inner face of vthe nut is provided with an angular recess 40 formedibetween the flanges providing the flat faces 37 and 38.v Fitted in this recess is positioned a locking 2plate 41 limited to about 240' of rotary movement relative to the casing by a projection 42 depending from the casing and extending into a recess 43' formed in the periphery of the locking plate as shown in Figure 2. The locking plate is provided with a plurality of apertures 44 disposed concentrically of the axis of rotation of the nut and each designed to be engaged selectively by a set screw 45 passed through the nut, designed to-engage in one of the apertures 44 and with its inner end in bearing engagement with the outer side 39 of the casing.

In operation and assuming that the parts are in the position shown in Figure 1 it will be 'understood that if the spring bridge plate and the pole pieces are permanently magnetized or current is sent through the coil windings to form a magnet, in either case the magnet will act on the diaphragm and bow its center downwardly and towards the electromagnet as indicated in the exaggerated showing in Figure 4. It is understood that the greater the pull of the electromagnet the closer will the diaphragm center approach the ends of the pole pieces. It is desirable in devices of this character to bring the diaphragn quite close to the ends of the pole pieces but without actually touching. In similar devices now known the bowing of the diaphragm towards the fixed ends of the pole pieces will cause the outer edge of each pole piece to be further from the diaphragm than the edge nearest the center due to the curve assumed by the bowed diaphragm. This difierence in depth of the air gap will become more pronounced with increase of bowing of the diaphragm.

In adjusting the device herein disclosed it will be understood that as the diaphragm is brought into its progressively bowed position closer and closer to the electromagnet by the magnet pull thereof, the control nut is rotated clockwise so as to bring the electromagnet bodily away from the diaphragm, as is known in certain forms of these instructions. However, in the present disclosure not only will the electromagnet pole pieces be drawn away from the diaphragrn perpendicular to its plane but the active ends of these pole pieces will tend to lean towards each other and inoline towards the central part of the diaphragm as exaggeratedly indicated in the showing in Figure 4. The resiliency of the bridge is selected so that the bowing of the bridge by the mechanical adjustment of the governing' screw and nut will be app-roximatfely the same as the bowing of the diaphragm under the influence of the electromagnet acting on the same. lt will thus be seen that as both the diaphragm and the bridge are bowed along substantially the same degree of are the ends of the pole pieces will likewise maintain their position squarely facing the part of the diaphragm opposite the same. ln this way the air gap between each pole piece end and the diaphragm will be maintained constant, or at least substantially constant, in the different adjusted positions of the diaphragm/and pole pieces.

As the ends of/th pole pieces are free to move towards each other as indicated in Figure 4 it willfbe seen that the lines of force are shortenedI with increased distortion of the diaphragm and spring bridge. In this way the electromagnet acts more forcibly on the diaphragm when it is bowed, and at a time when such force is necessary, than the electromagnet would act when the diaphragm is less bowed and when less pulling force is required to hold it in its adjusted position. Should it be desired to adjust the-relation of the electromagnet relative to the diaphragm at any time, as when tuning the loud speaker, the operator makes the desired micrometrical advance or retreat of the ends of the pole pieces 'simply by an angular turn of the nut. ln the original setting of the instrument the plate 41 is disposed with the pin 42 at one end of the recess 40, limiting screw 45 is set in that aperture d4; which will cause the screw to engage the underside 39 of the casing when the nut has been rotated into poston to give the maximum possible approach of the pole pieces tothe diaphragm. ln general there is featured means for adjusting the permissible length of travel of the pole pieces axially towards the diaphragm and adjustable means for limiting such travel. By this means the pole pieces are locked against an accidental physical engagement with the diaphragm which engagement would Ybe very apt to damage if not destroy the flexible diaphragm.

While I have shown have pointed out in the annexed claims, certain novel features of my invention, it will be understood that various omissions, substitutons and changes in the form and details of the device illustrated and in its operation' may be made by those skilled in the art withand described, and

o ut departing from the spirit of the inven- 5 Having thus described my invention, li claim l. lin a device of the class described, the combination of a cup-shaped casing open at one end, a diaphragm marginally supported on the casing at said open end. said casing provided within the same with two diametrically spaced supports, a thin strip of spring metal bridged across the casing with its ends resting on said spaced supports, an electromagnet including lL-shaped' pole pieces each having one leg secured to the spring bridge and having their other legs extending laterally from the spring bridge and on opposite sdes of its center, the free ends of said laterally extending legs positioned close to but spaced from the diaphragm on opposite sides of its center, and a set screw extending through the casing and engaging said spring bridge to flex the same between its supported ends and thus cause the free ends of the pole pieces to move relative to each other.

2. ln a device of the class described, a diaphragm controlling unit comprising a thin sheet of spring metal adapted to be supported at its ends, with its central portion free to be 'flexed, a pair of pole pieces extending laterally from said sheet adjacent its center and co-acting therewith to form an electrolift r relative to the diaphragm.

magnet, and binding posts acting to secure the pole pieces to the spring metal sheet;

3. In a device of the class described, a diaphragm controlling unit oomprising a thin sheet of spring metal adapted to be sup orted at its ends, 'with its central portion ree to be flexed, a pair of pole pieces extending laterally from said sheet ad'acent its center and co-acting therewith to orm an electromagnet, binding posts acting to secure the pile pieces to the spring netal sheet, and a set screw secured at one end to the springsheet adjacent its center. I

4. An electromagnet mechanism comprising a spring bridge supported atopposite ends and having a flexible center, a pair of magnets secured to the bridge and having/ their poles extending laterally from the bridge from one side thereof and on opposite sides of said center, a diaphragm operatively disposed to be placed under tension by said magnet, and means engaging the center of said bridge for flexing the same and thus adjusting relative to each other the ends of the pole pieces which are nearest the daiphragm.

5. An electromagn'etc mechanism comprising a spring bridge supported at its ends and constituting a magnet, pole pieces projecting from adjacent the center of said magnetic bridge, a diaphragm facing the pole pieces and operatively controlled by their magnetic condition and means engaging the bridge between its supported ends for adjusting the pole pieces relative to each other and 6. In a deviceV of the class described, the combinaiton of a marginally supported diaphragm, a permanent magnet having two poles with their ends flat, facing the diaphragm and acting thereon electromagnetically to bow the diaphragm towards the poles, said oles spaced apart to provide an air gap there tween, means for mounting the pole pieces to provide movement between said flat ends and means for adusting the magnet to maintain the flat ends of the` poles parallel to the portions of the bowed dia-phragm opposite the respective fiat ends of the poles.

7. In a device ofthe class described, the combination of a circular diaphragm held at its margin, a magnet having its poles acting electromagnetically on the diaphragm adjacent its center to bow the same towards the magnet, a spring plate for mounting the poles for relative movement and control means acting on the spring plate for bowing the same into substantial parallelism with the part of the bowed diaphragm facing the same.

8. In a device of the class described, a marginal held Circular diaphragm, a fiat spring plate facing the diaphragm and supported at its ends, magnetic poles carried by the plate for bowing the center of the dia-phragm, the ends of said poles being movable relative to each other, and a set, screw engaging the spring adjacent its center for bowing the spring and .thus adjust the position of the ends of the poles relative to each other and to the diaphragm.

9. In a device of the class described, the combination of a cup-shaped casing open at one end, a. diaphragm marginally supported on the casing at said open end, said casing provided within the same with two diametrically spaced supports, a thin strip of spring metal bridged across the casing with its ends rest-ing on said spaced supports,an electromagnet including L-shaped pole pieces each having one` leg secured tolthe, spring bridge and having their other legs extending laterally from the spring bridge and on opposite tmV sides of its center, the free ends of said lat-' I erallyextending legs positioned close to but spaced from the diaphragm on o posite sides of its center, a set screw exten ing through the casing and engaging said spring bridge to flex the same between its supported ends and thus cause the free ends of the pole pieces to move relative to each other, and an adjustng nut external to the casing and engaging said set screw to control the flexing of the spring bridge.

10.'In a device of the class described, the combnationbf a cup-shaped casing open at one end, a daphragm marginally supported on the casing at said open end, said casing provded within the same with two diametrically spaced supports, a thin strip of spring metal bridged across the casing, with its ends resting on said spaced supports, an electromagnet including L-shaped pole pieces each having one leg secured to the spring bridge and having their other legs extending laterall from the spring bridge and on opposite sic es of its center, the free ends of said laterally extending legs posit-ioned close toI but spaced from the diaphragm on opposite sides of ts center, a set screw extending through the casing and engaging said spring bridge to 'flex the same between its supported ends and thus cause the free ends of the pole pieces to move relative to each other, an adjusting nut external to the casing and en aging said set screw to control the fiexing o the spring bridge, and means engaging the nut for lockmg the screw and thereby locking the spring bridge in i ts preset position.

11. In a device of theclass described, the combination of a mechanism containing casing, a diaphragm controlling electromagnet 12. In a device of the class described, the combination of a mechanism containing casing, a diaphragm controlling electromagnet including a spring-bridge mounted in the casing, a screw intruded loosely through the casing for bowing the spring bridge, a bearing nut threaded on the externally projecting end of the screw and providing an extensive.

bearing surface on the outside of the casing, a locking plate housed in the nut and a screw passed through the nut and plate and adapted to bear on the casing to limit the movement in one direction' of said electromagnet.

13. In a. device of the class described, the combination of a casing, a diaphragm, an electromagnet Vcontrolling vthe diaphragm and mea-ns for adjusting the electromagnet relative to the diaphragm, said means including a screw extending loosely into the same, a nut in threa-ded engagement with the screw and bearing on the outside of the casing, the side of the nut facing the casing provided with a peripheral groove, a locking plate positioned in said groove and having a limited rotary movement relative to the casing, said plate provided with a plurality of apertures and a set screw extending throughthe nut for selectively engaging in one of said apertures to limit the screw in its axially adjusted movement.

14. In a device of the class described, the combination of a mechanism containing casing, a diaphragm and an electromagnet contained in the casing and a non-rotating screw for setting the electromagnet relative to the diaphragm, said screw intruded loosely through the casing and a nut in threaded. engagement with the screw for advancing the same axially through the casing and providing a wide bearing and resilient engagement with the casing, and means acting on the nut for limiting the permissible advance of the 'electromagnet relative to the diaphragm.

Signed at New York, in the county of New York and State of New York, this U19th clay of February, A. D. 1925.

CHARLES MILTON HAYMAN. 

